When Mary Lennox's parents die in India, she is shipped back to England
to live on her uncle's estate, Misselthwaite Manor, in Yorkshire.
The place is pretty much run by the dreadful Mrs. Medlock, while Mary's
uncle travels compulsively. Lord Archibald Craven is trying to escape
the memories that linger there, of his wife who died in childbirth.

Mary is a sullen brat but she is largely ignored by Mrs. Medlock and
so has time to explore the many nooks and crannies of the manor.
She finds one room that looks just like her mother's did--it is of course
her aunt's--and there finds a large key. It turns out that
the key fits the door of a secret garden, which Lady Craven tended and
which is now kept locked and allowed to grow wild. Mary befriends
young Dickon, whose sister is a housemaid, and together they explore the
garden.

One night Mary determines to find the source of a mysterious crying
she's heard in the house, and when she eventually does she discovers her
cousin, Colin, who survived his mother but is now sickly, crippled and
confined to his room. He proves an even worse brat than she.
Their mutual stubbornness though proves a boon as she refuses to accept
Colin's self-pitying and rejects the idea that he's truly all that ill.
She sets her mind to showing him the garden, convinced that just getting
outside will do him good. Meanwhile, he threatens and commands the
staff until they allow him out of the house. Their visits to the
garden will in fact transform all of their lives in ways that will move
even the most jaded reader. No wonder it is such a beloved classic.